Urinary incontinence (UI) is defined as the complaint of any involuntary loss of urine. The most common type of UI is stress urinary incontinence (SUI), defined as the complaint of involuntary leakage on effort or exertion, or on sneezing or coughing. Overactive bladder (OAB) is a complex of symptoms that is characterized by urinary urgency, with or without urgency-associated UI. Both UI and OAB are more common in women than in men and their prevalence is increased with age. The UI affects up to 38% of women; while the OAB prevalence estimates are reaching 43%. These conditions are socially embarrassing, causing significant morbidity and quality of life impact.
The pelvic floor muscles (PFM) form the floor of the female pelvic basin and help maintaining continence by actively supporting the pelvic organs. In the older population, pelvic floor disorders represent the combination of neuro-urinary pathology, functional and cognitive impairments, and changing biomechanical conditions of tissues.
The female pelvic floor comprises the pelvic diaphragm muscles (pubococcygeus, puborectalis, and iliococcygeus, levator plate together known as the levator ani), pubovaginal and puboperineal muscles, urethral and anal sphincter muscles. Anatomically and functionally these muscle are interrelated with each other. Correct action of the pelvic floor muscles is described as a squeeze around the pelvic openings and an inward lift. The pelvic floor muscles function includes electrical signal transmission and a mechanical action (contraction). The pelvic floor disorders result from neuro-urinary pathology as well as muscle functional impairment due to changes in biomechanical properties of soft tissues with age. That is why pelvic floor muscles characterization and diagnosis must include biomechanical (force) measurements and electromyographic (EMG) measurements or better tactile and EMG imaging with improved spatial resolution.
The pelvic floor treatment options include surgery, sacral neuromodulation with implanted electrodes, electrical muscle stimulation, medications and physiotherapy. An invasive surgical approach is considered as the ultimate treatment. However, numerous patient reports of adverse events are associated with surgical mesh; these include vaginal extrusion, erosion, infection, pain, dyspareunia, lower urinary tract symptoms, recurrence of incontinence, urinary retention, and blood vessel injury. Implantation of electrodes for sacral neuromodulation is also considered an invasive procedure. Physical training and medications are often not effective for treatments of UI. The transvaginal electrical simulation demonstrated feasibility for UI and OAB treatments but lacks objective functional and anatomically-specific guidance to select precise location for the effective therapy. To date, there is no standardized, reproducible tool to accurately assess the pelvic floor muscles function in anatomically-specific manner, and to apply guided muscle stimulation for UI and OAB therapy.
Biofeedback with vaginal pressure measurements (air balloon or 1-2 pressure sensors) has been widely used in the treatment of pelvic floor dysfunctions, mainly by promoting patient learning about muscle contraction. However, its effectiveness remains poorly understood with some studies suggesting that biofeedback offers no advantage over the isolated pelvic floor muscle training.
Surface electromyography, as a diagnostic method for neurological disorders, is used to evaluate pelvic muscle activation patterns during muscle contraction in women with UI. Commercially available vaginal probes designed to record EMG from the pelvic floor muscles have numerous deficiencies in their design, such as problems with probe geometry, electrode size, location, and/or configuration. Many probe designs are prone to recording motion artifacts, crosstalk, and/or inappropriate EMG signals. The current art in the field indicates that their measurement accuracy and reproducibility are too low for the reliable characterization of the pelvic floor muscles conditions. There is therefore a need for an improved intravaginal EMG probe for use in research and clinical practice.
Electrical muscle stimulation (EMS) of pelvic floor muscles with intravaginal electrodes may help strengthening the urethral closure mechanism, which is necessary during SUI and inhibit spontaneous involuntary bladder contractions. The EMS has been found to improve strength and vascularity of various groups of muscles including external anal sphincter and mixed hemorrhoid disease. Nevertheless, some controversy exists on effectiveness of EMS as a stand-alone therapy for female SUI, which may be attributed by the inability to apply guided and targeted EMS.
Tactile Imaging is a medical imaging modality that translates the sense of touch into a digital image. The tactile image is a function of P(x,y,z), where P is the pressure on soft tissue surface under applied deformation and x,y,z are coordinates where pressure P was measured. Functional Tactile Imaging translates muscle activity into dynamic pressure pattern P(x,y,t) for an area of interest, where t is time and x,y are coordinates where pressure P was measured. Muscle activity may include: muscle voluntary contraction, involuntary reflex contraction, involuntary relaxation, or specific maneuvers (e.g Valsalva maneuver) [for further information see van Raalte H. Egorov V. Tactile imaging markers to characterize female pelvic floor conditions. Open Journal of Obstetrics and Gynecology 2015; 5: 505-515].
There is a need in imaging and quantitative assessment of pelvic floor muscles for the effective management of the disorders. Therefore is a need for improved methods and devices for vaginal tactile and electromyographic imaging, and guided female pelvic floor therapy in order to support a treatment therapy as well as to improve quality of life and reduce the negative psychological impact on patients needing pelvic floor treatment.